Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe a two-step strategy to alter any mouse locus repeatedly and efficiently by direct positive selection. Using conventional targeting for the first step, a functional neo gene and a nonfunctional HPRT minigene (the "socket") are introduced into the genome of HPRT- embryonic stem (ES) cells close to the chosen locus, in this case the beta-globin locus. For the second step, a targeting construct (the "plug") that recombines homologously with the integrated socket and supplies the remaining portion of the HPRT minigene is used; this homologous recombination generates a functional HPRT gene and makes the ES cells hypoxanthine-aminopterin-thymidine resistant. At the same time, the plug provides DNA sequences that recombine homologously with sequences in the target locus and modifies them in the desired manner; the plug is designed so that correctly targeted cells also lose the neo gene and become G418 sensitive. We have used two different plugs to make alterations in the mouse beta-globin locus starting with the same socket-containing ES cell line. One plug deleted 20 kb of DNA containing the two adult beta-globin genes. The other replaced the same region with the human beta-globin gene containing the mutation responsible for sickle cell anemia.
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PMID:Deletion and replacement of the mouse adult beta-globin genes by a "plug and socket" repeated targeting strategy. 793 10

Hydroxyurea (HU) is an effective therapeutic agent for patients with myeloproliferative disorders (MPDs) or sickle cell disease (SCD). Short-term HU toxicities primarily include transient myelosuppression, but long-term HU risks have not been defined. The mutagenic and carcinogenic potential of HU is not established, although HU has been associated with an increased risk of leukemia in some patients with MPD. In this study, 2 assays were used to quantitate acquired somatic DNA mutations in peripheral blood mononuclear cells (PBMCs) after in vivo HU exposure. The HPRT assay measures hypoxanthine phosphoribosyl transferase (hprt) mutations, while the VDJ assay identifies "illegitimate" T-cell receptor Vgamma-Jbeta interlocus recombination events. PBMCs were analyzed from patients with MPD, adults and children with SCD, and normal controls. MPD patients with prolonged HU exposure had numbers of DNA mutations equivalent to patients with low HU exposure or controls. Similarly, adults with SCD had equivalent numbers of DNA mutations regardless of HU exposure. Children with SCD and 30-month HU exposure had equivalent hprt(-) mutations but significantly more VDJ mutations (1.82 +/- 1.20 events per microg DNA) than children with 7-month HU exposure (1.58 +/- 0.87 events) or no HU exposure (1.06 +/- 0.45 events), P =.04 by analysis of variance. Taken together, these data suggest that the mutagenic and carcinogenic potential of in vivo HU therapy is low. Although increased numbers of illegitimate VDJ recombination events do not directly portend leukemia, young patients with SCD and HU exposure should be monitored serially for increases in DNA mutations.
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PMID:Acquired DNA mutations associated with in vivo hydroxyurea exposure. 1082 48